This study examines the relationship between Industry competition structure, market power, firm excessive and stock price crash risk of companies listed in Tehran Stock Exchange for the period 2006-2013. For this purpose, 120 companies were selected. To test the research hypotheses statistical software Eviews 7 combined data is used. This study is descriptive and correlational where data analysis is performed using multiple regression. The results show that there is a significantly negative relationship between industry competition and stock price crash risk Also the results showed that there is a significantly positive relationship between market power and firm excessive stock price crash risk. Finally, our results indicate that firm excessive crash risk plays a moderating role on the relationship between market power and the stock price crash risk. In this sense, the power of the market, stock price crash risk increases for big companies, but for small businesses, strong market power helps to reduce stock price crash risk.
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